1. Technical Field
The present invention relates, in general, to compounds that inhibit protein kinase activity, and to compositions and methods related thereto.
2. Description of the Related Art
Cancer (and other hyperproliferative diseases) is characterized by uncontrolled cell proliferation. This loss of the normal control of cell proliferation often appears to occur as the result of genetic damage to cell pathways that control progress through the cell cycle. The cell cycle consists of DNA synthesis (S phase), cell division or mitosis (M phase), and non-synthetic periods referred to as gap 1 (G1) and gap 2 (G2). The M-phase is composed of mitosis and cytokinesis (separation into two cells). All steps in the cell cycle are controlled by an orderly cascade of protein phosphorylation and several families of protein kinases are involved in carrying out these phosphorylation steps. In addition, the activity of many protein kinases increases in human tumors compared to normal tissue and this increased activity can be due to many factors, including increased levels of a kinase or changes in expression of co-activators or inhibitory proteins.
Cells have proteins that govern the transition from one phase of the cell cycle to another. For example, the cyclins are a family of proteins whose concentrations increase and decrease throughout the cell cycle. The cyclins turn on, at the appropriate time, different cyclin-dependent protein kinases (CDKs) that phosphorylate substrates essential for progression through the cell cycle. Activity of specific CDKs at specific times is essential for both initiation and coordinated progress through the cell cycle. For example, CDK1 is the most prominent cell cycle regulator that orchestrates M-phase activities. However, a number of other mitotic protein kinases that participate in M-phase have been identified, which include members of the polo, aurora, and NIMA (Never-In-Mitosis-A) families and kinases implicated in mitotic checkpoints, mitotic exit, and cytokinesis.
Pim kinases (e.g., Pim-1 kinase, Pim-2 kinase, Pim-3 kinase) are a family of oncogenic serine/threonine kinases. Pim-1 kinase is known to be involved in a number of cytokine signaling pathways as a downstream effector. Once activated, Pim-1 kinase causes progression of the cell cycle, inhibition of apoptosis and modulation of other signal transduction pathways, including its own. Pim-1 kinase is also known to effect activation of transcription factors such as NFAT, p100, c-Myb and Pap-1, and inhibition of others such as HP1. Normal expression of Pim-1 kinase is seen in cells of hematopoietic origin, such as fetal liver, thymus, spleen and bone marrow. Additionally, expression is seen in prostate and oral epithelial cells Pim-1 kinase is believed to be involved in the initiation or progression of malignant transformation leading to malignancies including Burkitt's lymphoma, prostate cancer, oral cancer and diffuse large cell lymphomas, among others.
Pim kinases also play a role in immune regulation. For example, enhanced Pim expression has been observed in a variety of inflammatory states. Pim-2 is also implicated in cytokine induced T-cell growth and survival. A recent publication (Jackson et al., Cell Immunology, 2012, 272, 200-213) demonstrated in vivo efficacy for a dual PIM-1 and PIM-3 inhibitor in a mouse inflammatory bowel disease model. Therefore, PIM kinases are attractive targets for various autoimmune and/or inflammatory diseases.
Based on their involvement in a number of human malignancies, there is a need for the rational design of specific and selective inhibitors for the treatment of cancer and other conditions that are mediated and/or associated with Pim kinase proteins. The present invention fulfills these needs and offers other related advantages.